Lamp voltage control device



Aug. 7, 1934.

A. B. FUL'LER 1,969,459

LAMP VOLTAGE CONTROL DEVICE Filed July 50, 1932 gnmntoz: AlberfiBluller,v

Patented Aug. 7, 1934 UNITED STATES LAMP VOLTAGE CONTROL DEVICE AlbertB. Fuller, Rochester, N. Y., assignor to Eastman Kodak Company,Rochester, N. Y., a corporation of New York Application Jul so, 1932,Serial No. 626,701 2 Claims. (01. 176-10) My invention relates broadlyto apparatus for controlling the resistance of an electrical circuit andmore particularly to an adjustable circuit arrangement for insuring thatthe desired voltage will be applied to a lamp when the lamp is includedin the circuit.

In certain types of photographic printers in which-the exposure iscontrolled by switching the printing lamp on and off it is highlydesirable that the lamp be energized to the same level for each andevery exposure. Due to variations in line voltage and the factundesirable to switch on the lamp except for making exposures, theoperator does not know what the voltage drop across the lamp will bewhen he makes an exposure and it is usually impossible to read a voltmeter connected across the lamp because of the short time intervalsinvolved.

One of the objects of my invention is to provide a circuit arrangementwhereby a resistance in the lamp circuit may be so adjusted that thedesired voltage drop across the lamp will be present when the lampcircuit is closed.

Another object of my invention is to provide an arrangement whereby theadjustment of a measurable circuit simultaneously adjusts the unknownlamp circuit according to the same law so that proper adjustment of oneinsures a proper setting of the other.

Other objects and advantages of my invention will appear from thefollowing description when read in connection with the accompanyingdrawing and its scope will be pointed out in the appended claims.

Referring to the drawing the single figure of which shows a circuitarrangement embodying my invention the reference character R1 designatesa lamp which it is desired to repeatedly energize with a predeterminedvoltage and which is adapted to be connected to a source of power 10through an adjustable resistance R and a push switch 11. ance R areconnected in parallel with an adjustable resistance r and an adjustablerheostat n which are connected across the source 10 during the entiretime the lamp is to be used. The resistances R and r are adjustable inunison in any suitable manner as by sliding contacts 14 and 15 carriedby a common member 16. In practice the resistance of the unit r shouldbe several times that of the unit R so as to lower the amount of energydissipated in it.

Initial adjustment is obtained by adjusting the rheostat r1 until thevoltage drop across it equals the voltage drop across the lamp R1. Thepush switch 11 is held closed during this adjustment and the voltagedrops may be compared by alternately connecting a voltmeter 12 acrossthe rheostat T1 and the lamp R1 by means of a that it is generally Thelamp R1 and its series resist-.

switch 13. This adjustment need be made but once for any one lamp.

After the initial adjustment has been made, the voltmeter 12 is leftconnected across the rheostat T1. The two series resistances R and r areadjustable in unison and so proportioned that throughout their rangesthe voltage drop across the rheostat 1'1 and the lamp R1 vary together,the relation between the various resistances being such that r/r1=R/R1.

In operation, the lamp circuit being open, the resistance r is adjustedto bring the voltage drop as indicated by the voltmeter 12 to thedesired value and since the resistance R is adjusted simultaneously withthe resistance 1' when the push switch 11 is closed the voltage dropacross the lamp R1 will be of the desired value.

From the above description it will be seen that with the apparatus of myinvention it is possible to know immediately beforehand whether or notthe desired voltage will be applied to the lamp when its circuit isclosed and to adjust the lamp resistance the proper amount tomakecertain that the lamp will be energized the desired amount forcorrect printing.

While I have described in detail one specific embodiment of myinvention, it will be obvious to those skilled in the art that variousmodifications will readily suggest themselves without departing from thespirit of my invention, the scope of which is pointed out in theappended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination an electrical source subject to voltage variations, alamp circuit and a rheostat circuit connected in parallel to saidsource, an adjustable resistance in each of the parallel circuits, andmeans for adjusting simultaneously the two resistances without varyingthe ratio between the total resistances in the two circuits. v

2. In combinatiomtwo parallel circuits adapted to'be connected to asource of electrical energy, one of said circuits being normally openand containing a lamp, 8. switch for closing the circuit through thelamp, the other of said circuits being normally closed and containing arheostat the resistance of which bears a definite relation to theresistance of said lamp, an adjustable resistance in each or saidcircuits, and means for adjusting said resistances in unison.

ALBERT B. FUILER.

